延长拖网伏季休渔期的渔业资源养护效应

海洋伏季休渔制度是当前中国最主要的渔业资源管理制度之一,并在实践中得到不断调整与完善,新的海洋伏季休渔制度已于2017年发布实施。为论证新制度延长拖网休渔期的渔业资源养护效应,本研究依据2015—2017年每年5月东海区拖网大面定点调查资料,利用Ricker动态综合模型,从拖网的渔获结构特征和带鱼(Trichiurus japonicus)的种群动力学过程视角开展了相应的量化分析研究。研究结果表明, 5月拖网利用主体为带鱼和小黄鱼(Larimichthys polyactis),带鱼和小黄鱼的性成熟比例分别为92.04%～95.57%和13.82%～29.55%,幼鱼比例分别为74.94%～88.90%和0.03%～4.19%;带鱼种群经过4.5个月的休渔,其单位补充量资源量、单位补充量渔获量和平均渔获质量与3.5个月休渔期相比较,分别增加了7.04%、8.96%和20.78%。以上结果表明,提前并延长拖网休渔期,东、黄海主要经济渔业资源带鱼与小黄鱼的产卵群体和幼鱼得到进一步保护,资源增殖效果随着休渔期的不断延长而增加,新制度的休渔时间设置更趋合理。但由于开捕后的带鱼与小黄鱼渔获仍主要以当龄鱼为主,有必要同时配套执行现已颁布的最小网目尺寸和开捕标准等其他渔业资源管理措施,以确保伏季休渔制度主导下的渔业资源养护效果能真正得到巩固,渔业资源的种群结构能够得到切实好转与不断合理化。     

Verification of mean volume backscattering strength obtained from acoustic Doppler current profiler by using sound scattering layer

ABSTRACT:   Acoustic Doppler current profilers (ADCPs) have recently been used to estimate the dynamic characteristics and biomass of sound scattering layers (SSLs) or swimming speed of fish schools and to analyze SSL spatial distribution or various behavior patterns. This paper shows that it is necessary to verify mean volume backscattering strength (MVBS, dB) values acquired from each beam for quantitative analysis of the spatial distribution or the biomass estimates of such specific targets as SSL or a fish school when using an ADCP. In this study, the SSL was selected to be a homogeneous density layer over a large area and two methods were used to verify the MVBS values from each beam of the ADCP. First, a mutual comparison among four beams was conducted after calculating MVBS from the measured echo intensity. Second, the MVBS values were verified using comparison between the calculated MVBS from the 153.6 kHz ADCP and MVBS from three frequencies of a well-calibrated scientific echosounder. Moreover, the dominant scatterers (euphausiids) were collected by a framed midwater trawl. From these samples, biological data were used to identify the different frequency characteristics between two systems, using a distorted-wave Born approximation (DWBA) theoretical backscattering model in order to assess the averaged target strength and target strength TS differences for the three frequencies.     

Evaluation of an experimental Aeromonas salmonicida epidemic in chinook salmon, Oncorhynchus tshawytscha (Walbaum)

To determine the dynamics of the transmission of Aeromonas salmonicida ssp. salmonicida infection, chinook salmon, Oncorhynchus tshawytscha, were exposed to bacteria by cohabitation. The latent period (time between exposure and infectivity) was determined by exposing a group of chinook salmonid fingerlings to A. salmonicida by bath, then, at daily intervals, by holding five exposed (donor) fish with approximately 50 naive fish for 24 h. The latent period was 3 days post-infection and the time period between the initial exposure to bacteria and the beginning of bacterial shedding was 4.5 days for the same animals. The prevalence and intensity of infection in the donor fish, to which recipient fish were exposed, i.e. the level of exposure, was highly correlated with the development of disease in recipient (susceptible) chinook salmon (r2 = 0.57). An experiment was conducted to determine the daily progress of infection and development of a furunculosis epidemic among recipient fish by cohabiting a single exposed fish with 43 unexposed salmon. At daily intervals, all fish (in seven treatment tanks and one control tank daily) were sacrificed and tested for the presence of A. salmonicida in the kidney (n = 3520). Over 10 days, mean prevalence among recipient fish reached 75% and disease related mortality exceeded 50%. Bacterial concentrations in the water continued to increase over the duration of the experiment in concert with the number of infected animals present in the population.     

水流作用下悬跨管道振动的实验研究

为了比较得到水下管道安全悬跨长度的判别条件并验证其合理性。使用弹性力一重力相似理论设计模型实验,管道两端均采用固定约束,管道与水流之间的角度分别为90°、75°、60°、45°和30°,悬跨管长分别为1．00m、0．81m、0．73rn、0．70rn。通过实验比较fn≥10fs、fn≥（0．7）-1．fs、fn=5fs（fn为悬跨管道固有频率;六为水流激振频率）3种条件对悬跨管道振动的判别情况。研究表明,根据fn=5fs,即约化速度K=1的条件,计算得到的临界长度较安全、合理,并由fn=5f条件给出了不同管径、壁厚和流速条件下管道临界长度的规律图,研究结果可为水下悬跨管道的安全评价提供借鉴。（图3,表2,参13）     

Does larval mortality influence population dynamics? An analysis of North Sea herring (Clupea harengus) time series

The daily mortality rates of North Sea herring early‐stage larvae are found to vary over decades. Larval abundance data were used with a spatio‐temporal oceanographic model to reconstruct temperature histories of the observed larvae. The histories were used in conjunction with a temperature‐based growth model to estimate larval age. Mean daily mortality rates were then estimated for the four spawning components (Downs, Banks, Buchan and Orkney/Shetland) using the vertical life table approach, which considers instantaneous abundances across all ages rather than following distinct cohorts. All spawning components, but especially Downs (in the south), exhibited a steady rise in mortality associated with increasing population size. In addition, the three northern components shared a distinct trend in mortality that was significantly correlated with ambient water temperatures experienced by the larvae during the respective time periods after hatching. This trend was also significantly negatively correlated with the residuals of the whole stock‐recruitment relationship. These findings were generally robust to assumptions about growth and hatch length of larvae. The compensatory increase in productivity in the late 1980s and poor recruitment since 2000 coincide with changes in the mortality of larvae younger than 30 days post hatch and covary with larval density and temperature. Thus we suggest that the mortality of early‐stage larvae does impact on the population dynamics in North Sea herring in its current productivity regime, implying a critical period in the determination of year class strength.     

应用RFV评价鄂尔多斯荒漠草原优势牧草营养价值

将采自内蒙古鄂尔多斯地区的禾本科牧草3种、豆科牧草3种和菊科牧草3种分别于6月、7月和9月刈割晾干,共制得27个样本。通过应用饲料相对指数(RFV)进行综合评定可知:将6月、7月和9月分别刈割的同一品种牧草混合后,品质最好的为中苜2号,其次是沙打旺,再次是沙蒿,最差的是花棒;同种牧草不同刈割期比较可知:对于禾本科牧草来说,针茅、冰草和中苜2号在不同刈割期营养价值的大小顺序为6月7月9月;对于豆科牧草来说,花棒、沙打旺在不同刈割期营养价值的大小顺序为6月7月9月,但草木樨在不同刈割期营养价值的大小顺序则为6月9月7月;对于菊科牧草来说,沙蒿、猪毛蒿、籽蒿在不同刈割期营养价值的大小顺序为7月6月9月。     

长期膜下滴灌棉田土壤水盐分布变化及其对棉花生长影响

以库尔勒市包头湖农场长期膜下滴灌棉田为研究对象,通过连续3年棉田整个生育期土壤水分和盐分含量的测定,对长期膜下滴灌棉田土壤水盐分布变化及其对棉花生长影响进行了研究。结果表明:各年份土壤平均含水率在整个生育期呈降增降的趋势,平均含盐量呈增降增的趋势;20~50cm土层土壤含水率较高,土壤盐分在30~50cm土层聚积;土壤含盐量高于0.51%时产量开始受到抑制,高于1.79%时棉花产量将降低为零。     

渭北旱塬“赤霞珠”葡萄浆果膨大期光合特性研究

【目的】分析山地和平地赤霞珠葡萄(Vitis viniferaL.cv Cabernet Sauvignon)的光合作用特性,为形成持续发展的葡萄与葡萄酒生产体系提供依据。【方法】采用LI-6400便携式光合测定仪,分析了陕西省耀州区山地和平地两个葡萄园中赤霞珠葡萄浆果膨大期叶片的净光合速率、蒸腾速率、胞间CO2浓度和气孔导度等生理生态指标。【结果】山地和平地赤霞珠葡萄的净光合速率日变化相似,均表现出双峰曲线,首峰出现在上午10:00,次峰小于首峰,出现在下午15:00以后;山地和平地赤霞珠葡萄叶片的净光合速率、蒸腾速率、胞间CO2浓度和叶绿素含量差异显著,水分利用效率和气孔导度差异不显著,在光响应曲线内的最大净光合速率和表观量子效率分别为14.40μmol/(m2.s),0.036和12.58μmol/(m2.s),0.035,在CO2响应曲线内的最大净光合速率和羧化效率分别为23.99μmol/(m2.s),0.061和18.43μmol/(m2.s),0.059,模拟曲线的R2值都大于0.94;不同海拔条件下净光合速率与PAR、蒸腾速率和气孔导度呈极显著正相关,与胞间CO2浓度呈显著负相关。【结论】山地条件下葡萄具有高光效和高产的光合特性。     

Flumequine depletion from muscle plus skin tissue of gilthead seabream (Sparus aurata L.) fed flumequine medicated feed in seawater at 18 and 24 °C

We examined flumequine depletion from muscle plus skin of gilthead seabream held in seawater at 18 and 24 °C. Seven groups of 10 fish each were sampled at intervals ranging from 24 to 168 h after in-feed administration of flumequine at 35 mg/kg/day for 5 days. Muscle plus skin tissue samples were analyzed for flumequine by high-performance liquid chromatography and fluorescence detection (HPLC-SFD). Parent flumequine concentrations declined rapidly from muscle plus skin after dosing with elimination half-lives of t_1/2=22.14 and 21.43 h at 18 and 24 °C, respectively. Withdrawal periods for the maximum residue limit (MRL) of 600 μg/kg flumequine in muscle plus skin at 95% tolerance limit were 106.08 and 75.84 h at 18 and 24 °C, respectively, after treatment.